CO2 can be produced by a lot of metabolic reactions and is the end point of
numerous metabolisms. The high performances of continuous flow ratio mass
spectrometry (CF-IRMS) allow measuring very low levels of C-13 enrichment f
rom very-small analytical samples. These CO2 microgenerator technology can
be used in a lot of biological protocols, this paper presents the inverse i
sotopic dilution method used for the determination of C-13 from CO2 generat
ed by cells ( poly-morpho nuclear cells) or microorganisms. The determinati
on of amino acids using the (CO2)-C-13, generated by the reaction with ninh
ydrin from micro samples is also presented. These examples show that microg
enerators of CO2 can be used for the study of a lot of biological or chemic
al systems in so far as they can produce CO2.